| Disease (causal agent) | Symptoms | Survival of pathogen and effect of environment | Comments on control |
|---|---|---|---|
| Alternaria leaf spot* and branch rot (Alternaria saponariae) |
Gray-brown leaf or petal spots with purple margins. Black spore masses form in spots. Branch rot starts at nodes and girdles stem. | In infected plants and debris. Airborne spores. Moist conditions for 8 to 10 hours required for infection. | Provide good air circulation and keep humidity low. Irrigate in early morning. Do not wet foliage with irrigation water. During periods of high humidity, protect plants with iprodione, mancozeb, or chlorothalonil. |
| Bacterial wilt * (Pseudomonas caryophylli) |
Sudden wilting of tops or individual branches. Basal stem cracks. Roots may be rotted. Vascular discoloration in stems is yellowish to brown. The outer layer (epidermis) separates easily from stem, which is sticky to the touch. | Infected plants and debris. Bacteria spread in water. Favored by high temperatures. | Use disease-free cuttings and treat soil as above. Bacteria can spread quickly. Avoid use of cutting dips and avoid splashing water. Break cuttings from stock plants. Disinfect tools. |
| Calyx rot (Stemphylium botryosum) |
Rot starts at tip of calyx and progresses towards base. | In old leaves, stems, and debris. Favored by high humidity. | Same as Greasy blotch. Harvest regularly. |
| Fairy-ring leaf spot (Cladosporium echinulatum) |
Conspicuous tan spots with concentric rings. Margin of spot may be red. Dark spores form in spots. | Infected plants and debris. Airborne spores. Favored by wet weather. | Provide good air circulation and keep humidity low. Irrigate in early morning. Do not wet foliage with irrigation water. Protect foliage with mancozeb. |
| Fusarium bud rot (Fusarium tricinctum) |
Outwardly normal buds are brown and decayed inside. Cottony white growth and plump white mites may be visible. | Fungus carried by grass mite, Pediculopsis graminum. | Destroy infected buds. Control mites. Do not bring field-grown carnations into greenhouse. Control weeds outside growing area. |
| Fusarium stem rot (Fusarium avenaceum, F. culmorum, F. graminearum) |
Stem rotted at soil line and high up on plant. Roots and base of stem rotted. Tops wilt and die. Pink cushions of spores may form at base of plant on decayed tissues. Common as a cutting rot. | In soil and plant debris. Spores spread in water. Also favored by warm, humid conditions. Also favored by high N fertilization and high N:K ratio. | Use clean cuttings and rooting medium. Spray cuttings in rooting medium with thiophanate-methyl. |
| Fusarium wilt * (Fusarium oxysporum f. sp. dianthi) |
Yellow, wilted branches frequently occur on one side at first. Vascular discoloration is dark brown. Root system usually remains intact. In late stages, stem develops a dry, shredded rot. Infected parts die. | Soil and infected plants. Spores spread in water. Favored by soil temperatures 75°F and above. Restricted below 60°F. | Plant resistant cultivars. Use disease-free cuttings planted in treated soil. Steam soil in raised beds at 140°F for at least 30 minutes. Solarize soil or fumigate with chloropicrin. Adjust soil pH to 6.5 to 7.0. |
| Moderately resistant: | Ace, Apache, Barsemi Yasmino, Big Red, Comanche, Corona, Exquisite Select, Felicia, Fiesta, Georgia Ann, Jolievette, Lucy Carrier, Maman, Mei-Sciang, Orchid Beauty, Pallas, Shiro, Silvery Pink, Sweetheart, White Elegance | ||
| Highly resistant: | Barbi, Candy Maj, Capello, Carbasio, Improved Lilac, Juanita, Lady Di, Light Pink Marble, Maiko, Maj Pink, Meiling, Melody, Moonlight, Picotee Orange, Scarlett Elegance, Siri #1, White Melody | ||
| Gray mold * (Botrytis cinerea) |
Fuzzy gray fungal spores form on soft, brown, decayed blossoms and can move into plant parts wherever blossoms touch them. | In plant debris. Airborne spores. Favored by high moisture conditions and low temperatures. | Remove old flowers from growing area. Maintain horizontal air movement. Lower humidity where possible. Mist blooms with iprodione or fenhexamid. |
| Greasy blotch (Zygophiala jamaicensis) |
Greasy-appearing spots on leaves with radiating weblike margins. Pimpling of infected areas. | In infected plants and debris. Favored by high humidity. Not too common. | Provide good air circulation and keep humidity low. Irrigate in early morning. Do not wet foliage with irrigation water. |
| Phialophora wilt (Phialophora cinerescens) |
Gradual wilting of plants; leaves become straw colored. Not one-sided as Fusarium wilt may be. Brown discoloration of vascular system. Little or no tissue rotting in late stages. Uncommon. | Soil and infected plants. Spores spread in water. Favored by cool soil temperatures. | Use disease-free cuttings and treat soil as above. |
| Phytophthora stem rot * (Phytophthora parasitica) |
Stem rotted at soil line. May be mistaken for Rhizoctonia stem rot. | In soil and plant debris. Favored by warm, moist soil and poor drainage. | Steam or fumigate soil. Drench at planting with oomycete (water mold) specific fungicide. |
| Pythium root rot * (Pythium spp.) |
Plants are stunted, particularly in lower, poorly drained areas. Rootlets rotted. | Soilborne. Common in most soils. Favored by poor drainage, low spots, excessive irrigation. | Steam or fumigate soil (see Fusarium wilt). Drench plants with oomycete (water mold) specific fungicide periodically, depending on severity of disease. Make first application at planting. |
| Rhizoctonia stem rot (Rhizoctonia solani) |
Stem rotted at soil line. Rot progresses from the outside. Entire plant wilts and dies. Dark fungal strands and sclerotia may be visible with a hand lens. | Soilborne; plant debris. Favored by warm, moist conditions. | Steam rooting medium and soil. Use PCNB before transplanting, or spray base of transplant with iprodione. |
| Rust * (Uromyces dianthi) |
Small pustules of powdery brown spores. Spores are airborne. | Carried over only on living plants. Favored by moist conditions. | Use resistant cultivars or protect plants in problem areas with myclobutanil or mancozeb. |
| Virus or viruslike diseases | Symptoms | Host range and natural spread | Comments on control |
| Mottle
(Carnation mottle virus) |
Faint leaf mottle or no symptoms. Common in virtually all carnation cultivars. | Handling and cutting knife. Not transmitted by insects. May be spread in drainage water. | Reduce spread of mottle by disinfecting tools between blocks of plants and several times a day. Obtain virus-free plants. |
| Etched ring | Rings usually oval or elongated; rarely concentric on older leaves and stems. Symptoms may be slight in young cuttings. No obvious effect on plant vigor. | Aphids. Not spread by handling. | Obtain virus-free plants. Control aphids. |
| Necrotic fleck | Reddish purple necrotic flecks, streaks, or spots appear in leaves. Symptoms are masked at low temperatures. | Aphids. | Obtain virus-free plants. Control aphids. |
| Ring spot | Small 0.5- to 1-inch rings; sometimes concentric. Chlorosis, mottling, and distortion of young leaves. Plants obviously stunted. | Cutting knife and handling. Insect vectors unknown. | Same as for mottle. |
| Vein mottle (not common in California) |
Young leaves exhibit a vein clearing, which develops into chlorotic spots and patterns that mostly follow veins. Symptoms tend to disappear on old leaves. | Aphids. Not spread by handling or cutting knife. | Obtain virus-free plants. Control aphids. |
| * For additional information, see section on Key Diseases. |